1. Field of the Invention
The present invention relates to a waking degree maintaining apparatus for discriminating a drop in waking degree of a person, and presenting a stimulus according to the drop in waking degree, thereby maintaining the person in a waking state of a predetermined level.
2. Description of the Related Art
When a person performs monotonous work for a long period of time, he or she experiences a drop in waking degree (attentiveness), and recovers a waking state after a while. There is no method to quantitatively measure such a rhythm of the waking state in which normal and low waking levels repetitively appear, although it can be obscurely recognized.
It is known that the waking degree drops due to work or an operation of a vehicle for a long period of time, and the reaction time at that time is prolonged. However, no method for quantitatively measuring how much the reaction time is prolonged is available.
When a drop in waking degree of a person is estimated based on, e.g., the blinking frequency, a predetermined trigger value is set in eye movement data. When the data exceeds the trigger value, it is determined that an eye movement occurs, and the number of times of eye movements is counted. As the trigger value, an eye movement waveform for about 1 to 5 minutes is observed, and a value with which a stable blinking frequency can be measured is experimentally set.
In recent years, the necessity for quantitative determination of the waking state, i.e., a technique for quantitatively recognizing the time characteristics of a drop in waking degree, and preventing the drop in waking degree, has increased. However, a method for detecting and determining the drop in waking degree or the state of tension itself with high precision has not been found yet.
For example, in the measurement of the blinking frequency, the above-mentioned method is an effective method capable of obtaining a stable result when a base line fluctuation is small, and when the measurement time is short enough to be able to ignore the influence of a time in which electrodes for the measurement become adapted to a living body and are degraded. However, in a long-time measurement, since the base line fluctuates, the initially set trigger value often becomes ineffective, and the trigger value must be re-set.
When the time waveform of the eye movement is measured using, e.g., a computer, the waveform is differentiated, and time-series data of the differential values is similarly triggered to measure the blinking frequency. However, the same problem as described above is posed, or the influence of a disturbance such as an electrode vibration which often occurs upon measurement under vibration cannot be eliminated.